①
at weekends(没指定哪个)
on the weekend(指定)
②
on weekdayson the weekend指定什么。？是特指哪天？那在工作日不可以说at weekdays?I never work at weekends .周末我从不工作。
What are you doing on the weekend ?这个周末你准备干什么？(指定哪个周末)
不可以用at weekdays,只能 on weekdaysthanks